Black cars show everything, and it's REALLY hard not to introduce micro-marring during routine washing, which is especially visible on darker colored cars.
Some basic things...are you using grit guards in your buckets? Even though Yvan was famous for his single bucket, reuse-the-solution-a-lot-of-times, I consider it "best practice" to use a rinse bucket with a grit guard (to which I add some ONR, about 1/4 normal, to keep from diluting things too much), and I use a fresh batch of solution every time, no matter how much I have left. I also wash my wash media (in the washing machine) after every use (I don't use sponges like the BRS, generally, I like the microfiber-covered sponges).
Then there is preparation--do you do any kind of pre-rinse? A pressure washer would be ideal but it kind of defeats the purpose of a rinseless wash. Most people do a pre-rinse/pre-soak with some sort of waterless wash, or more concentrated solution of rinseless, using a pump-up sprayer. I never find this to be very effective. I have been intrigued by an online personality that posted a video of a Harbor Freight airless paint sprayer to pre-rinse with rinseless solution from a bucket, but I haven't tried that yet.
Here's the most important thing...when your car is dirty it generally has grit that is "stuck" to the paint. This can be dust from the air, brake dust from your car or other cars, dirt from the road, etc. If you drive in the rain/snow, there is all kinds of grit splashed up that gets stuck to the paint. You don't want to grind this dirt/grit into the paint during the wash process. Hence the idea of a pre-soak/pre-rinse to loosen that stuff up first, and it's very important that you use a minimal amount of pressure as you agitate and dislodge this debris, and make sure you rinse it off the media thoroughly before going back to the panel.
One technique that I have used is to use one side of the media very lightly on a panel, then turn the media over for another pass with more pressure now that the initial dirt has been removed. Of course there is also the "single-use media" technique, which is usually a pile of towels or mitts, that only get used once and not returned to the car surface after they get dirty. This obviates the need for a rinse bucket or any grit guards, you simply have a solution bucket with clean media, you use it until it's dirty, then throw it in a bucket (to be washed later), and move on to clean media. In this way no dirt is reintroduced to the surface...unfortunately for me, I have never been able to get this method to work to my satisfaction, and I always go back to using two buckets and one piece of media.
Bottom line is it's almost impossible to not introduce some micromarring through routine washing, which is why most enthusiasts do a light polish on their car on some periodic basis. However, you can minimize that marring with good technique.